Executive Summary: Key Legal and Evidentiary Issues

• Characterization of the CNESST’s right to intervene under article 13 LITAT and whether an intervention filed after a worker–employer settlement is necessarily out of time.
• Determination that the applicable standard of review is reasonableness, even though procedural fairness and natural justice are invoked, because the core issue is the TAT’s interpretation of its constitutive statute.
• Evaluation of whether refusing to hear the CNESST before rejecting its late intervention breached the duty of procedural fairness (audi alteram partem).
• Assessment of whether a very brief one-page letter from the TAT met statutory obligations to provide written, motivated reasons (article 47 LITAT and article 13 LJA).
• Legal effect of the parties’ “entente” and request for a return to conciliation on the notion of “end of the inquiry and hearing” and on the stability of settlements in workers’ compensation disputes.
• Consequences of treating the TAT’s refusal to register the intervention as effectively final for the CNESST, yet still upholding it as reasonable and dismissing the judicial review with costs.

Factual background

David Vaillancourt was an employee of A.C.I.E.R.S. inc. (“ACIERS”) when he suffered a work accident on 18 October 2021. Following this workplace injury, the Commission des normes, de l’équité, de la santé et de la sécurité du travail (CNESST) recognized his claim and began paying benefits under Quebec’s occupational health and safety scheme. On 11 May 2023, the CNESST accepted the opinion of the Bureau d’évaluation médicale on Mr. Vaillancourt’s permanent impairment and functional limitations and issued a decision to that effect. The same day, it rendered a separate decision fixing his indemnity for bodily injury, relying in particular on an assessment by Dr. Demers. At the joint request of the worker and the employer, these two decisions were reviewed by the CNESST and confirmed on 24 July 2023.
Administrative appeals before the TAT

After the CNESST’s review and confirmation, the worker contested the 24 July 2023 decision before the Tribunal administratif du travail (TAT) on 14 August 2023, giving rise to TAT file 1332883. On 17 August 2023, the employer filed its own contestation of the same review decision, which became file 1333402. These contests placed before the TAT the extent of Mr. Vaillancourt’s permanent impairment, his functional limitations, and the related benefits. The CNESST, although notified, did not immediately intervene in those early files.
Subsequent CNESST decisions on capacity and rehabilitation

On 2 February 2024, the CNESST concluded that Mr. Vaillancourt’s functional limitations prevented him from resuming his pre-accident job or any other suitable position available at ACIERS. As a result, it terminated its intervention with that employer. At the employer’s request, the CNESST reviewed this decision and confirmed it on 8 May 2024. ACIERS then contested the review decision before the TAT on 4 July 2024, which created file 1375298. Later, on 20 December 2024, the CNESST issued two further decisions: first, it determined that Mr. Vaillancourt was capable of performing a suitable job as a “gérant de commerces de détails” (retail store manager) with an estimated annual earning capacity of 34,000 dollars; second, it accepted to reimburse housekeeping services for heavy household chores, given his ongoing physical limitations. On 13 March 2025, at the request of both the worker and the employer, the CNESST reviewed and confirmed these two decisions.
Later contests and CNESST interventions in other files

The 13 March 2025 review decision was then contested by the worker at the TAT on 17 March 2025, giving rise to file 1410868. In this newer file, the CNESST promptly advised the TAT and the parties on 28 March 2025 that it intended to intervene. On 6 May 2025, the employer also contested the same 13 March 2025 review decision, leading to file 1417989. Again, the CNESST notified the TAT and the parties of its intention to intervene in that file on 12 May 2025. In these two most recent files, therefore, the CNESST formally became an intervening party in time. By contrast, in the earlier files (1332883, 1333402 and 1375298), it had not yet exercised its statutory right to intervene by the time settlement discussions between the worker and the employer crystallized.
Settlement between the worker and the employer

On 22 October 2025 at 18:13, counsel for ACIERS filed a “Formulaire de demande de retour en conciliation” via the TAT’s electronic portal. In that form, she indicated that a settlement (“entente”) had been reached between the parties and requested that the matter be returned to conciliation in several files, including 1332883, 1333402 and 1375298. On 23 October 2025, the worker’s representative, with the employer’s consent, asked the TAT to postpone the hearing scheduled for 30 October and to return all of the relevant files, including those three, to conciliation. By 24 October 2025, the TAT’s docket (plumitif) for file 1332883 had been updated to include the entry “Règlement intervenu” (settlement reached), reflecting the Tribunal’s acknowledgment that the underlying dispute between the worker and the employer had been resolved.
The CNESST’s late attempt to intervene

On 24 October 2025, after the settlement had been brought to the TAT’s attention, the CNESST sent an intervention notice covering files 1332883, 1333402 and 1375298. That same day, counsel for ACIERS and for Mr. Vaillancourt both wrote to the TAT to oppose the intervention, arguing that it was inadmissible because the settlement had already been concluded on 22 October 2025. The CNESST then requested that the TAT hear it specifically on whether the intervention was late or not. Instead of convening a hearing or inviting written submissions, the TAT’s coordinating administrative judge, Julie Falardeau, issued a formal letter dated 24 October 2025 addressed to the CNESST’s representative. In this letter, she acknowledged receipt of the intervention notice, stated that it was late because it had been filed after a settlement had intervened between the parties on 22 October, and announced that the Tribunal would therefore not register the intervention. The letter also explained that, depending on the nature of the settlement, the TAT would either receive notices of discontinuance or be asked to approve an agreement. In the latter case, the agreement would be submitted to an administrative judge for approval under article 23 of the Loi instituant le Tribunal administratif du travail (LITAT), and the CNESST would then be able to use any recourses provided by law against that eventual decision.
Statutory framework: article 13 and article 23 LITAT

Article 13 LITAT governs the CNESST’s intervention rights in matters dealt with by the health and safety division of the TAT. It provides that the TAT will notify the CNESST upon receiving an initiating pleading and that the CNESST must send its file to the Tribunal and the parties within a fixed delay. Crucially, the third paragraph stipulates that the CNESST may intervene “at any time until the end of the inquiry and the hearing” by sending an intervention notice to the TAT and the parties, at which point it becomes a party to the contestation. Article 23 LITAT regulates settlements and agreements. It requires that any agreement in a health and safety matter be recorded in writing and, in this division, be formally approved (entériné) by a TAT member, but only if it is consistent with the law. Once approved, the agreement becomes the Tribunal’s decision and ends the case. Together, these provisions create a structure in which the CNESST has a broad but time-limited right to intervene, while settlements between worker and employer remain subject to the TAT’s oversight for legal conformity.
The judicial review application before the Superior Court

On 18 November 2025, a TAT conciliator finally sent the 24 October 2025 letter-decision to the CNESST’s representative, who had been waiting for it. On 25 November 2025, the CNESST filed an application for judicial review in the Superior Court of Quebec (District of Trois-Rivières), seeking to have the TAT’s decision of 24 October 2025 annulled. The CNESST argued first that the TAT had violated principles of natural justice and procedural fairness, particularly the right to be heard, by refusing its intervention without giving it an opportunity to be heard on the issue of lateness. It invoked not only general common-law fairness principles but also article 35 LITAT and articles 9, 10 and 12 of the Loi sur la justice administrative (LJA), which codify the obligation to conduct a fair, impartial hearing and to give parties a chance to present and challenge evidence. Second, the CNESST alleged that the TAT’s decision was inadequately reasoned, contrary to article 47 LITAT and article 13 LJA. It maintained that a brief letter merely stating that the intervention was “tardy” without detailed legal reasoning or clear reference to the statutory framework did not meet the duty to provide written, motivated reasons. In addition, the CNESST contended that the decision was reviewable despite being interlocutory in form, because it was effectively final as to its own ability to participate in the approval (entérinement) of the settlement and to influence the terms that might affect benefits it would later administer.
Standard of review: correctness or reasonableness

A key legal issue before Justice Nancy Bonsaint concerned the applicable standard of review. The CNESST argued that, under prevailing case law, alleged breaches of procedural fairness are always reviewed on a correctness standard. It relied on authority stating that courts owe no deference where the issue is whether the tribunal has complied with rules of natural justice. ACIERS and the TAT responded that, in this particular case, the fairness complaint was inseparable from the TAT’s interpretation of its own constitutive statute—specifically the meaning of “end of the inquiry and the hearing” in article 13 LITAT. They pointed to appellate case law recognizing that when procedural fairness is tied directly to how a tribunal reads its home statute, the applicable standard can remain reasonableness. Justice Bonsaint accepted this view. She held that the TAT’s refusal to register the intervention depended on its understanding of when an “inquiry and hearing” effectively ends once a settlement has been concluded and reported to the Tribunal. Because that is a matter of interpreting the TAT’s enabling statute, the presumption of reasonableness review under the Supreme Court’s Vavilov framework was not displaced. She therefore applied the reasonableness standard both to the fairness allegations and to the adequacy-of-reasons argument.
Reasonableness of the TAT’s interpretation and decision

In assessing reasonableness, the Court examined whether the TAT’s decision, taken as a whole, was intelligible, justified and defensible in light of the facts and the governing law. On the factual side, the TAT knew that an agreement had been reached between the worker and the employer on 22 October 2025 and that the parties had formally reported this to the Tribunal, requesting a return to conciliation. It also knew that the CNESST’s intervention notice arrived only on 24 October 2025, after the settlement. On the legal side, the TAT applied article 13 LITAT, which limits the CNESST’s intervention to the period before the end of the inquiry and the hearing. Justice Bonsaint considered prior Court of Appeal jurisprudence where it had been held reasonable for a specialized tribunal in occupational health and safety matters to treat the conclusion of a settlement as marking the end of the inquiry and hearing for purposes of similar intervention rules. Against this backdrop, she found it rational for the TAT to read article 13 as meaning that, once the Tribunal acknowledges a settlement and the file is effectively removed from the hearing list for conciliation and eventual approval, there is no longer an inquiry or hearing to intervene in. It followed that an intervention filed after that point could be treated as late on its face. The Court therefore concluded that the TAT’s refusal to register the CNESST’s intervention was a defensible application of its home statute and consistent with the legislative objective of preserving the stability of worker–employer settlements.
Procedural fairness and the right to be heard

On the fairness issue, the CNESST argued that it should at least have been granted an opportunity to explain why its intervention ought not to be considered out of time or why the notion of “end of the inquiry and the hearing” did not apply at the settlement stage. Justice Bonsaint acknowledged that, under article 35 LITAT and the LJA, parties generally have the right to present their case and be heard before a decision affecting their interests is made. She also noted, however, that the CNESST enjoys a very broad statutory privilege: it may intervene at any time up to a clear cut-off date, and it had actual notice of the litigation and of a hearing date but chose not to intervene earlier. The judge accepted the TAT’s characterization of its decision as one of case management, taken on the basis of the uncontested chronology in the Tribunal’s own record. In that procedural posture, and given the limited nature of the question—whether a post-settlement intervention could logically be considered timely—she found no serious procedural unfairness in deciding on the written record alone, without an additional hearing. The Tribunal’s choice not to invite further submissions was, in her view, within the range of reasonable procedures open to a specialized administrative body managing its own docket.
Adequacy of reasons and statutory duty to give written, motivated decisions

The CNESST further submitted that the TAT’s one-page letter failed to meet statutory duties under article 47 LITAT and article 13 LJA, which require decisions that end an affair to be written and motivated, and to be expressed in clear and concise terms. Justice Bonsaint agreed that the letter was brief and did not explicitly cite article 13 LITAT or case law. Nonetheless, she emphasized that motivation must be assessed in context. The letter identified the specific files, acknowledged the intervention notice, recited the key fact of a prior settlement dated 22 October, drew the conclusion that the intervention was late, and indicated the procedural consequences (non-registration of the intervention and the treatment of the settlement). When read alongside the statutory text and the established meaning of “end of the inquiry and the hearing,” the reasons allowed both the parties and a reviewing court to understand why the intervention was refused. Accordingly, the Court held that, while the TAT might have offered fuller analysis, the decision did not suffer from the kind of serious reasoning defect that would render it unreasonable under Vavilov.
Outcome and successful party

Having found that the TAT’s handling of the CNESST’s late intervention was within the bounds of reasonableness, both in its interpretation of article 13 LITAT and in its approach to procedural fairness and reasoning, the Superior Court dismissed the application for judicial review. The formal disposition states that the Court “rejects the application for judicial review, with costs.” As a result, the TAT’s 24 October 2025 decision stands, the CNESST remains excluded as an intervening party in files 1332883, 1333402 and 1375298, and the settlement between Mr. Vaillancourt and ACIERS may proceed to approval in accordance with article 23 LITAT. The successful parties in this judgment are therefore the Tribunal administratif du travail, supported in practice by the mis en cause David Vaillancourt and A.C.I.E.R.S. inc., while the CNESST is the unsuccessful applicant. The judgment orders costs against the CNESST but does not specify the exact monetary amount of costs or any other monetary award, so the total sum in favour of the successful parties cannot be determined from this decision alone.